Power consumption and bandwidth limitation in electrical interconnects is a bottleneck to further improve performance and efficiency of charge-based large scale integrated circuits (ICs), such as those based on a complementary metal-oxide-semiconductor (CMOS) platform and architecture. In charge-based systems, electrical charge is used to represent state variables such as digital bits (e.g., high charge represents a digital high, low charge (or no charge) represents a digital low). Transmitting charge-based representations of digital bits at higher data rates requires additional power and bandwidth, which may not be available.
Spin-based systems can potentially address the limitations of charge-based electrical systems based on CMOS ICs at least with respect to power and architectural constraints of transmitting digital bits at higher data rates. In spin-based systems, an electron spin is used represent state variables. For example, through spin-transfer torque (STT), spins of electrons in one direction in a spin-polarized current cause a magnetic moment of a free layer of a magnetoresistive device (e.g. a magnetic tunneling junction (MTJ), a giant magnetoresistive (GMR) device) to align (e.g., magnetic moment to align) in the same direction (e.g., parallel magnetization state), and spins of electrons in the other direction in the spin-polarized current cause the free layer of the magnetoresistive device to align in the opposite directions (e.g., anti-parallel magnetization state).
In the spin-based systems, the magnetization state of the magnetoresistive devices is indicative of the digital bit. For example, a parallel magnetization state represents a digital low, and an anti-parallel magnetization state represents a digital high, or vice-versa. The magnetization state is read out from the measurement of the resistance value of the magnetoresistive devices, low resistance for the parallel magnetization state and high resistance for the anti-parallel magnetization state.